Both natural and synthetic elastomers usually require the use of antiozonants to improve resistance to the attack of ozone in the finished rubber products. Certain waxy materials, added in excess of their solubility in rubbers, will bloom to the surface after vulcanization. The surface film of wax provides protection from the atmosphere so long as the film remains. Paraffin, microcrystalline waxes and various combinations of waxes are examples of such waxes and are commonly used in combination with antiozonants. Paraffin waxes bloom very quickly whereas microcrystalline blends bloom more slowly. Commonly a combination of waxes are used.
Natural and synthetic elastomers typically require the use of processing aids to assist mechanical blending and compounding. Materials such as mixtures of oil soluble sulfonic acids of high molecular weight with a high boiling alcohol, paraffin oils, blends of sulfonated petroleum products and selected mineral oils are conventionally used as processing aids. Additional examples include petroleum, paraffinic and vegetable oils, coal tar, petroleum residues or pitches and naturally occurring or synthetic resins. One advantage in using processing aids is they assist the incorporation of fillers and other ingredients with low power requirements since the processing aids reduce internal friction in calendering and extrusion. By reducing the amount of friction during compounding, the temperature of the rubber will remain lower and thus minimize the possibility of scorch.